Deficiency of a triterpene pathway results in humidity-sensitive genic male sterility in rice

Zheyong Xue,Dan Liu,Xia Xu,Xiaoquan Qi,Binbin Zhao,Xiaoning Wang,Yuan Zhou,Lixin Duan,Yingchun Zhang

doi:10.1038/s41467-018-03048-8

Abstract

In flowering plants, the pollen coat protects the released male germ cells from desiccation and damage during pollination. However, we know little about the mechanism by which the chemical composition of the pollen coat prevents dehydration of pollen grains. Here we report that deficiency of a grass conserved triterpene synthase, OsOSC12/OsPTS1, in rice leads to failure of pollen coat formation. The mutant plants are male sterile at low relative humidity (RH < 60%), but fully male fertile at high relative humidity (>80%). The lack of three major fatty acids in the pollen coat results in rapid dehydration of pollen grains. We show that applying mixtures of linolenic acid and palmitic acid or stearic acid are able to prevent over-dehydration of mutant pollen grains. We propose that humidity-sensitive genic male sterility (HGMS) could be a desirable trait for hybrid breeding in rice, wheat, maize, and other crops.

Highlights

IntroductionThe pollen coat protects the released male germ cells from desiccation and damage during pollination
In flowering plants, the pollen coat protects the released male germ cells from desiccation and damage during pollination
OsOSC12 and its encoded protein are expressed in tapetal cells at relatively late stages of anther development[14,15] from S8 to S11 (Fig. 1 and Supplementary Figs. 1–3)

Summary

Introduction

The pollen coat protects the released male germ cells from desiccation and damage during pollination. We report that deficiency of a grass conserved triterpene synthase, OsOSC12/OsPTS1, in rice leads to failure of pollen coat formation. The mutant plants are male sterile at low relative humidity (RH < 60%), but fully male fertile at high relative humidity (>80%). We propose that humidity-sensitive genic male sterility (HGMS) could be a desirable trait for hybrid breeding in rice, wheat, maize, and other crops. Conditional male sterility systems facilitate breeding of hybrid varieties with yield advantages in many crops[1]. To more fully exploit the potential of two-line hybrid breeding systems, additional conditional male sterility systems could be beneficial. Mutants that are deficient in pollen coat formation may have conditional male sterile phenotypes[18]. OsOSC12 is a grass-species-specific triterpene synthase that is expressed in the anther[22]

Methods

Results

Conclusion